Struct ipworks::MCast

Properties   Methods   Events   Config Settings   Errors  

The MCast struct is used to multicast User Datagram Protocol (UDP) datagrams to multicast-capable hosts in multicast-capable subnets. It can act both as a client and a server and can communicate with any number of hosts simultaneously, as well as generate and receive broadcast packets.

Syntax

ipworks::MCast

Remarks

The MCast struct is very similar to UDP, except for some additional properties that provide support for multicast datagrams. To send datagrams to a multicast group, simply assign the address of the group to remote_host. To receive datagrams from one or more groups, assign the group addresses to multicast_group one by one (after the struct is activated). time_to_live allows you to specify how many subnets a packet should be allowed to receive. receive_interface and send_interface allow you to select the network interface for multicast operations.

The struct is activated/deactivated through the active property. This property enables or disables sends or receives. The data can be sent in the same way as UDP, by calling the send method with a Text parameter. The destination is specified using the remote_host and remote_port properties. Inbound data are received through the on_data_in event.

Object Lifetime

The new() method returns a mutable reference to a struct instance. The object itself is kept in the global list maintained by IPWorks. Due to this, the MCast struct cannot be disposed of automatically. Please, call the dispose(&mut self) method of MCast when you have finished using the instance.

Property List

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The following is the full list of the properties of the struct with short descriptions. Click on the links for further details.

Method List

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The following is the full list of the methods of the struct with short descriptions. Click on the links for further details.

Event List

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The following is the full list of the events fired by the struct with short descriptions. Click on the links for further details.

Config Settings

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The following is a list of config settings for the struct with short descriptions. Click on the links for further details.

accept_data property (MCast Struct)

This property indicates whether data reception is currently enabled.

Syntax

fn accept_data(&self ) -> Result<bool, IPWorksError> 

Default Value

true

Remarks

This property indicates whether data reception is currently enabled. When false, data reception is disabled and the on_data_in event will not fire. Use the pause_data and process_data methods to pause and resume data reception.

This property is read-only.

Data Type

bool

active property (MCast Struct)

This property indicates whether the struct is active.

Syntax

fn active(&self ) -> Result<bool, IPWorksError> 

Default Value

false

Remarks

This property indicates whether the struct is currently active and can send or receive data. Use the activate and deactivate methods to control whether the struct is active.

This property is read-only.

Data Type

bool

local_host property (MCast Struct)

The name of the local host or user-assigned IP interface through which connections are initiated or accepted.

Syntax

fn local_host(&self ) -> Result<String, IPWorksError> 
fn set_local_host(&self, value : &str) ->  Option<IPWorksError> 
fn set_local_host_ref(&self, value : &String) ->  Option<IPWorksError> 

Default Value

""

Remarks

This property contains the name of the local host as obtained by the gethostname() system call, or if the user has assigned an IP address, the value of that address.

In multihomed hosts (machines with more than one IP interface) setting LocalHost to the IP address of an interface will make the struct initiate connections (or accept in the case of server structs) only through that interface. It is recommended to provide an IP address rather than a hostname when setting this property to ensure the desired interface is used.

If the struct is connected, the local_host property shows the IP address of the interface through which the connection is made in internet dotted format (aaa.bbb.ccc.ddd). In most cases, this is the address of the local host, except for multihomed hosts (machines with more than one IP interface).

NOTE: local_host is not persistent. You must always set it in code, and never in the property window.

Data Type

String

local_port property (MCast Struct)

This property includes the User Datagram Protocol (UDP) port in the local host where MCast binds.

Syntax

fn local_port(&self ) -> Result<i32, IPWorksError> 
fn set_local_port(&self, value : i32) ->  Option<IPWorksError> 

Default Value

0

Remarks

This property must be set before MCast is activated (active is set to True). It instructs the struct to bind to a specific port (or communication endpoint) on the local machine.

Setting it to 0 (default) enables the system to choose a port at random. The chosen port will be shown by this property after the connection is established.

This property cannot be changed once the struct is active. Any attempt to set this property when the struct is active will generate an error.

This property is useful when trying to send data to services that require a trusted port on the client side.

Data Type

i32

loopback property (MCast Struct)

This property enables or disables loopback of data sent to the multicast group.

Syntax

fn loopback(&self ) -> Result<bool, IPWorksError> 
fn set_loopback(&self, value : bool) ->  Option<IPWorksError> 

Default Value

true

Remarks

This property enables or disables loopback of data sent to the multicast group. Setting this property to False disables loopback of data sent through the struct (normally loopback is enabled). This property is directly related to the IP_MULTICAST_LOOP socket option.

Data Type

bool

multicast_group property (MCast Struct)

This property includes the multicast group to join or leave.

Syntax

fn multicast_group(&self ) -> Result<String, IPWorksError> 
fn set_multicast_group(&self, value : &str) ->  Option<IPWorksError> 
fn set_multicast_group_ref(&self, value : &String) ->  Option<IPWorksError> 

Default Value

""

Remarks

This property contains the multicast group to join or leave. Multicast groups are joined by assigning values to this property after the struct is activated. More than one group may be joined at the same time. To define which interface to use, the receive_interface property is used.

Determining whether a group is left or joined is done by setting the first letter of multicast_group to "-" or "+". The default operation is join.

To remove the struct from a multicast group once it is joined, simply assign this groupname (address) to multicast_group prefixed by a minus sign "-".

Example. Joining/Leaving Groups:

MCastControl.Active = true MCastControl.MulticastGroup = "+231.31.31.31" MCastControl.MulticastGroup = "+232.32.32.32" MCastControl.MulticastGroup = "-232.32.32.32" MCastControl.MulticastGroup = "-231.31.31.31"

Data Type

String

receive_interface property (MCast Struct)

This property includes the interface with which to receive multicast packets. If empty, the default is used.

Syntax

fn receive_interface(&self ) -> Result<String, IPWorksError> 
fn set_receive_interface(&self, value : &str) ->  Option<IPWorksError> 
fn set_receive_interface_ref(&self, value : &String) ->  Option<IPWorksError> 

Default Value

""

Remarks

This property is useful when there is more than one network interface, and the one used for receiving multicast datagrams is not the default. If you wish to set an interface other than the system default, provide the IP address of the interface to be set.

This property is used along with the multicast_group property to join one or more multicast groups. The joining is done after the struct is activated by assigning proper values to multicast_group.

Data Type

String

remote_host property (MCast Struct)

This property includes the address of the remote host (multicast group).

Syntax

fn remote_host(&self ) -> Result<String, IPWorksError> 
fn set_remote_host(&self, value : &str) ->  Option<IPWorksError> 
fn set_remote_host_ref(&self, value : &String) ->  Option<IPWorksError> 

Default Value

""

Remarks

This property contains the address of the remote host (multicast group). To send a multicast datagram, specify a remote_host value in the range of 224.0.0.0 to 239.255.255.255. These addresses are reserved as multicast addresses by IP.

Data Type

String

remote_port property (MCast Struct)

This property includes the User Datagram Protocol (UDP) port on the remote host.

Syntax

fn remote_port(&self ) -> Result<i32, IPWorksError> 
fn set_remote_port(&self, value : i32) ->  Option<IPWorksError> 

Default Value

0

Remarks

This property contains the UDP port on the remote_host to send UDP datagrams to.

A valid port number (i.e., a value between 1 and 65535) is required.

Data Type

i32

send_interface property (MCast Struct)

This property includes the interface from which multicast packets are sent. If empty, the default is used.

Syntax

fn send_interface(&self ) -> Result<String, IPWorksError> 
fn set_send_interface(&self, value : &str) ->  Option<IPWorksError> 
fn set_send_interface_ref(&self, value : &String) ->  Option<IPWorksError> 

Default Value

""

Remarks

This property is useful when there is more than one network interface, and the one used for sending multicast datagrams is not the default. If you wish to set an interface other than the system default, provide the IP address of the interface to be set.

Data Type

String

time_to_live property (MCast Struct)

This property includes the maximum number of subnets that a multicast datagram can traverse.

Syntax

fn time_to_live(&self ) -> Result<i32, IPWorksError> 
fn set_time_to_live(&self, value : i32) ->  Option<IPWorksError> 

Default Value

7

Remarks

This property contains the maximum number of subnets that a multicast datagram can traverse. The default value for this property is 7. This is an arbitrary value. You need to specify a value suitable for your application.

Multicast datagrams with this property set to 0 are not transmitted on any subnetwork. Multicast datagrams with this property set to 1 are delivered only on the local network. Multicast datagrams with this property set to greater than 1 may be delivered to more than one subnetwork if one or more multicast routers are attached to the first-hop subnetwork.

A multicast router does not forward multicast datagrams with destination addresses between 224.0.0.0 and 224.0.0.255, inclusive, regardless of their time_to_live. This particular range of addresses is reserved for the use of routing protocols and other low-level topology discovery or maintenance protocols, such as gateway discovery and group membership reporting.

Data Type

i32

activate method (MCast Struct)

This method enables sending and receiving of data.

Syntax

fn activate(&self) -> Result<(), IPWorksError>

Remarks

This method enables sending and receiving of data. When called, the component will create a communication endpoint (socket) that can be used for sending and receiving User Datagram Protocol (UDP) datagrams.

config method (MCast Struct)

Sets or retrieves a configuration setting.

Syntax

fn config(&self, configuration_string : &str) ->  Result<String, IPWorksError>

Remarks

config is a generic method available in every struct. It is used to set and retrieve configuration settings for the struct.

These settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the struct, access to these internal properties is provided through the config method.

To set a configuration setting named PROPERTY, you must call Config("PROPERTY=VALUE"), where VALUE is the value of the setting expressed as a string. For boolean values, use the strings "True", "False", "0", "1", "Yes", or "No" (case does not matter).

To read (query) the value of a configuration setting, you must call Config("PROPERTY"). The value will be returned as a string.

deactivate method (MCast Struct)

This method disables sending and receiving of data.

Syntax

fn deactivate(&self) -> Result<(), IPWorksError>

Remarks

This method disables sending and receiving of data. When called, the component will destroy the existing socket and disable data communications.

do_events method (MCast Struct)

This method processes events from the internal message queue.

Syntax

fn do_events(&self) -> Result<(), IPWorksError>

Remarks

When do_events is called, the struct processes any available events. If no events are available, it waits for a preset period of time, and then returns.

pause_data method (MCast Struct)

This method pauses data reception.

Syntax

fn pause_data(&self) -> Result<(), IPWorksError>

Remarks

This method pauses data reception when called. While data reception is paused, the on_data_in event will not fire. Call process_data to reenable data reception.

process_data method (MCast Struct)

This method reenables data reception after a call to PauseData .

Syntax

fn process_data(&self) -> Result<(), IPWorksError>

Remarks

This method reenables data reception after a previous call to pause_data. When pause_data is called, the on_data_in event will not fire. To reenable data reception and allow on_data_in to fire, call this method.

NOTE: This method is used only after previously calling pause_data. It does not need to be called to process incoming data by default.

reset method (MCast Struct)

This method resets the struct.

Syntax

fn reset(&self) -> Result<(), IPWorksError>

Remarks

This method will reset the struct's properties to their default values.

resolve_remote_host method (MCast Struct)

This method resolves the hostname in RemoteHost to an IP address.

Syntax

fn resolve_remote_host(&self) -> Result<(), IPWorksError>

Remarks

This method resolves the hostname specified by remote_host to an IP address. The resolved value is available in the remote_host property after this method returns.

In most cases, calling this method is not necessary; the struct will resolve the hostname automatically when needed. If DelayHostResolution is true, this method may be called to manually resolve remote_host, if desired.

send method (MCast Struct)

This method sends data to the remote host.

Syntax

fn send(&self, text : &[u8]) -> Result<(), IPWorksError>

Remarks

This method sends data to the remote host.

send_bytes method (MCast Struct)

This method sends data to the remote host.

Syntax

fn send_bytes(&self, data : &[u8]) -> Result<(), IPWorksError>

Remarks

This method sends data to the remote host. Calling this method is equivalent to calling the send_bytes/send_text method.

send_text method (MCast Struct)

This method sends data to the remote host.

Syntax

fn send_text(&self, text : &str) -> Result<(), IPWorksError>

Remarks

This method sends data to the remote host. Calling this method is equivalent to calling the send_bytes/send_text method.

on_data_in event (MCast Struct)

This event is fired when data are received.

Syntax

// MCastDataInEventArgs carries the MCast DataIn event's parameters.
pub struct MCastDataInEventArgs {
  fn datagram(&self) -> &[u8]
  fn source_address(&self) -> &String
  fn source_port(&self) -> i32
}

// MCastDataInEvent defines the signature of the MCast DataIn event's handler function.
pub trait MCastDataInEvent {
  fn on_data_in(&self, sender : MCast, e : &mut MCastDataInEventArgs);
}

impl <'a> MCast<'a> {
  pub fn on_data_in(&self) -> &'a dyn MCastDataInEvent;
  pub fn set_on_data_in(&mut self, value : &'a dyn MCastDataInEvent);
  ...
}

Remarks

The on_data_in event is fired every time a new datagram is received.

datagram contains the packet as sent by the remote host.

source_address contains the IP number (Internet address) of the remote host, and source_port contains the port from which the packet originated.

NOTE: Events are not re-entrant. Performing time-consuming operations within this event will prevent it from firing again in a timely manner and may affect overall performance.

on_error event (MCast Struct)

Fired when information is available about errors during data delivery.

Syntax

// MCastErrorEventArgs carries the MCast Error event's parameters.
pub struct MCastErrorEventArgs {
  fn error_code(&self) -> i32
  fn description(&self) -> &String
}

// MCastErrorEvent defines the signature of the MCast Error event's handler function.
pub trait MCastErrorEvent {
  fn on_error(&self, sender : MCast, e : &mut MCastErrorEventArgs);
}

impl <'a> MCast<'a> {
  pub fn on_error(&self) -> &'a dyn MCastErrorEvent;
  pub fn set_on_error(&mut self, value : &'a dyn MCastErrorEvent);
  ...
}

Remarks

The on_error event is fired in case of exceptional conditions during message processing. Normally the struct fails with an error.

The error_code parameter contains an error code, and the description parameter contains a textual description of the error. For a list of valid error codes and their descriptions, please refer to the Error Codes section.

on_ready_to_send event (MCast Struct)

This event is fired when the struct is ready to send data.

Syntax

// MCastReadyToSendEventArgs carries the MCast ReadyToSend event's parameters.
pub struct MCastReadyToSendEventArgs {
}

// MCastReadyToSendEvent defines the signature of the MCast ReadyToSend event's handler function.
pub trait MCastReadyToSendEvent {
  fn on_ready_to_send(&self, sender : MCast, e : &mut MCastReadyToSendEventArgs);
}

impl <'a> MCast<'a> {
  pub fn on_ready_to_send(&self) -> &'a dyn MCastReadyToSendEvent;
  pub fn set_on_ready_to_send(&mut self, value : &'a dyn MCastReadyToSendEvent);
  ...
}

Remarks

The on_ready_to_send event indicates that the underlying Transmission Control Protocol (TCP)/IP subsystem is ready to accept data after a failed send.

Config Settings (MCast Struct)

The struct accepts one or more of the following configuration settings. Configuration settings are similar in functionality to properties, but they are rarely used. In order to avoid "polluting" the property namespace of the struct, access to these internal properties is provided through the config method.

UDP Config Settings

Socket Config Settings

Base Config Settings

Trappable Errors (MCast Struct)

MCast Errors

SSL Errors

TCP/IP Errors